Electric valve circuits



Sept. 26, 1944. 1 LEVOY JR 2,359,130

' ELECTRIC VALVE CIRCUIT Filed Feb. 13, 1942 PHASE SHIFTER 5%? 29Inventor: Louis G. Levos JP.

b 17 AMA 5 His Attorheg.

Patented Sept. 26, 1944 ELECTRIC VALVE CIRCUITS Louis G. Levoy, Jr.,Schenectady, N. Y., assignor to General Electric Company, a corporationof New York Application February 13, 1942, Serial No. 430,783

6 Claims.

My invention relates to electric valve circuits and more particularly tocontrol circuits for electric valve apparatus of the type employing anionizable medium, such as a gas or a vapor.

Electric valve means of the type employing an ionizable medium, such asa gas or a vapor and utilizing a control member of the immersionignitertype associated with the cathode have found rather general applicationin systems which are required to deliver current of predeterminedmagnitude to a load circuit, such as a welding circuit, from analternating current supply circuit. Various types of control orexcitation circuits have been provided for electric valve equipment ofthis nature. One type of circuit rather generally employed is that inwhich the excitation circuit is responsive to the anode voltage of theassociated electric valve, and wherein the energizing or ignitioncurrent for the electric valve means is derived from the supply circuit.In accordance with the teachings of m invention described hereinafter, Iprovide a new and improved circuit wherein the range of operation ofcontrol or excitation circuits of this nature and the flexibility ofcontrol are substantially increased.

It is an object of my invention to provide new and improved electricvalve translating apparatus.

It is another object of my invention to provide a new and improvedelectric control or excitation circuit for electric valve means of thetype employing an ionizable medium and using an immersion-ignitercontrol member.

Briefly stated, in the illustrated embodiment of my invention I providea new and improved excitation circuit for electric valve translatingsystems which may comprise a pair of reversely con nected electricvalves connected between an alternating current supply circuit and atransformer which in turn is connected to the load circuit. Anode-typestarting or excitation circuits are connected between the anodes of eachof the electric valve means and the associated immersion-igniter controlmember and are provided with rectifiers or electric discharge deviceswhich are controlled to transmit excitation or ignition current to thecontrol members at predetermined times during a cycle of voltage of thesupply circuit, and to control thereby the conductivity of the electricvalve means and control the amount of current transmitted to the loadcircuit. An impedance element such as a capacitance is connected inseries relation. with the anode-cathode circuits of the electric valvemeans and preferably connected across at least a portion of the primarywinding means to obtain a substantiall low impedance path to the flow ofignition or excitation current, thereby assuring the transmission of thepredetermined critical minimum value of current to the control membersirrespective of the impedanc of the load circuit and irrespective of thetime during the cycle at Which the electric discharge devices arerendered conducting.

For a better understanding of my invention, reference may be had to thefollowing drawing taken in connection with the accompanying drawing, andits scope will be pointed out in the appended claims. The single figureof the drawing diagrammatically illustrates an embodiment of myinvention as applied to an electric valve system for energizing awelding circuit.

Referring now to the single figure of the drawing, I have thereillustrated my invention as applied to an electric valve translatingsystem for energizing a variable impedance load circuit I, such as awelding circuit, from an alternating current supply circuit 2 through apair of reversely connected electric valve means 3 and 4 and atransforming means, such as a transformer 5, having primary windingmeans 6 and secondary winding means 1 connected to the load circuit 1.

The electric valve means 3 and 4 are each preferably of the typeemploying an anode 8, a cathode 9 and having an immersion-ignitercontrol member ll] associated with the cathode 9. The cathode 9 may be amercury pool into which the control member 10 extends. The controlmember ID is constructed of a material such as boron carbide or siliconcarbide which has an electrical resistivity substantially large comparedwith that of the associated mercury and is effective to initiate an arcdischarge between the anode 8 and cathode 9 upon the transmission of apredetermined critical value of current to the control member. I provideexcitation circuits l l and [2 associated with electric valve means 3and 4, respectively, and which are of the type responsive to therespective anode voltages of the electric valve means. Excitationcircuits II and I2 comprise unidirectional conducting devices orrectifiers, such as electric discharge devices I3 and M which areconnected to the anodes 8 of electric valve means 3 and 4 throughresistances I5 and I6, respectively. If desired, fuses I! and I8 may beconnected in series relation with the electric discharge devices 13 and14 to open and prevent operation of the excitation circuits in the eventthe excitation current tends to exceed a predetermined value.

Electric discharge devices I3 and I4 may also be of the type comprisingan ionizable medium and each of these discharge devices may comprise acontrol grid I9 which are normally biased to maintain the dischargedevices nonconducting. The electric discharge devices are renderedconducting at predetermined times during predetermined cycles of voltageof supply circuit 2 by control and timing circuits and 2|. The controlcircuits 2!] and 2| in turn may be energized from a master control andtiming circuit 22 which maybe energized from the alternating currentsupply circuit 2 through a suitable phase shifting means 23.

The control and timing circuit 22 may be any of the types now well knownin the art and may control the system to effect intermittentenergization of the load circuit I or to effect a single energization ofthe load circuit for a predetermined number of half cycles of voltage ofsupply circuit 2.

For the purpose of diagrammatically illustrating my invention, I havechosen to show the timing circuit 22 as comprising a transformer 24having a primary winding 25 and secondary windings 26 and 2'! which areconnected tocontrol circuits 2!] and 2|, respectively. Suitable negativeunidirectional biasing potentials may be impressed on the control gridsI9 of the electric discharge devices I3 and I4 by batteries 23 and 29,respectively. Transformers 24, if desired, may be of the saturable typewhich induces in windings 23 and 21 voltages of peaked wave form inorder that the discharge devices I3 and I4 are rendered conducting atprecise instants during cycles of voltage of supply circuit 2.Energization of circuits 23 and 2| may be controlled by suitable meanssuch as a relay 38 which is connected across the secondary windings 26and 21 of transformer 24. The relay 33 may be provided with an actuatingcoil 3| and normally closed contacts 32a and 321) which are connectedacross the secondary windings 21 and 26 through current limitingresistances. The actuating coil 3| may be energized intermittently fromcircuit 33 to effect intermittent energization of the load circuit I, ormay be energized for a predetermined interval of time in response to asingle circuit controlling operation to effect a single energization ofthe load circuit I.

In order to provide a relatively low impedance path for the flow ofexcitation current to the control members ID of electric valve means 3and 4, irrespective of the impedance of the load circuit I andtransformer 5 and irrespective of the time during the cycle of voltageof supply circuit 2 at which the electric discharge devices I3 and I4are rendered conducting, I connect in circuit with control members it]and electric discharge devices I3 and I4 a suitable impedance means suchas capacitance 34 which may be connected across the primary windingmeans 6 of the transformer 5. If desired, of course, the capacitance 34may be connected across only a portion of the primary winding means. Inthis manner positive ignition of electric valve means 3 and 4 is assuredeven though the electric valve system is operated within that regionwherein the control voltages provided by circuits 23 and 2| are withinthe latter portion of the respective positive half cycles ofanode-cathode voltage applied to electric valve means 3 and 4. The

sesame capacitance 34, by virtue of its nature, assures the transmissionof sufficient current to the control members I0 and at the same timewill, of course, prevent the transmission of an excessive amount ofcurrent since the current transmitted therethrough will decrease as thecharge on the capacitance increases.

While I have chosen to represent the impedance means which is connectedacross the rimary winding means as being a capacitance, it will beunderstood that other impedance means of suitable character may also beused in place of a capacitance. An important consideration is that theimpedance of the path provided in series relation with the anode-cathodecircuit of electric valve means 3 and 4 be of such value that theexcitation current transmitted to control members It will be ofsufficient magnitude to render the electric valve means conductiveirrespective of the time during the positive half cycles of appliedanode-cathode voltage at which the electric discharge devices I3 and I4are rendered conductive. Of course, the only limitation on the region ofthe positive half cycles during which suitable excitation current istransmitted to the control members is the magnitude or value of voltagerequired to transmit the critical control member current. By providing apath in parallel with the primary winding means, a substantially greatercurrent may be transmitted through the control member for the same valueof anode-cathode volt- The operation of the embodiment of my inventionshown in the single figure of the drawing will be explained byconsidering the system when it is operating to effect energization ofthe load circuit I from the supply circuit 2. More particularly, it willbe assumed that it is desired to effect energization of the load circuitI for a predetermined number of half cycles of the voltage of supplycircuit 2 in response to a single circuit controlling operation, such asthat which will be obtained by energizing circuit 33 for a predeterminedperiod of time.

Upon energization of actuating coil 3| of relay 30, contacts 32a, and32b of this relay are opened, causing the transmission of alternatingvoitages of peaked wave form to control circuits 20 and 2| fro-mtransformer 24. Electric discharge devices I3 and I4, which havepreviously been maintained nonconducting by virtue of the biasingpotentials furnished by batteries 28 and 29, will now be renderedconducting at predetermined times established by the phase position ofthe voltages of peaked wave form.

If it be assumed that it is desired to transmit current of relativelysmall magnitude to the load circuit I, the phase shifter 23 is adjustedso that the electric discharge devices I3 and I4 are rendered conductingwithin the latter portion of the respective positive half cycles ofanode-cathode voltage applied to electric valve means 3 and 4. If it beassumed further that the discharge device I3 is rendered conductingfirst, a circuit is completed for the energization of the control memberIii of the electric valve means 3 through a circuit including the lowerterminal of supply circuit 2, fuse I7, resistance I5, the anode-cathodecircuit of electric discharge device I3, control member ID and cathode 9of electric valve means 3, capacitance 34 and the upper terminal of thesupply circuit 2. It will, therefore, be appreciated that a path ofpredetermined impedance is provided to assure the transmission to thecontrol member ill a current'which is at least equal to the criticalcurrent required to initiate an arc discharge between the anode 8 andcathode 9 of electric valve means 3. Of course, during the succeedinghalf cycle of voltage of supply circuit 2 the control member In ofelectric valve means 4 will be energized through a corresponding circuitincluding the capacitance 34.

It will be appreciated that in this manner great accuracy may beobtained in control of the magnitude of the current transmitted to theload circuit I, even though the system is adjusted to effect thetransmission of only a relatively small current to the load circuit. Inthis manner, the range of application of anode-responsive type firingcircuits for electric valve means employing immersion-igniter controlmembers has been enlarged to permit application to that type of loadwhich requires wide ranges of current control; Furthermore, the accuracyof load current control is not sacrificed.

The use of a capacitance in circuit with the anode-cathode circuits ofthe electric valve means 3 and 4, while it assures the transmission ofthe necessary or desired current to render the electric valve meansconductive throughout substantially the entire positive half cycles ofapplied anode-cathode voltage irrespective of the phase setting or thephase position of the voltages of control circuits and M, also serves toprevent the transmission of excessive current to control members I0, orthe transmission of current during an extended period of time to thecontrol members. It will be appreciated that as the capacitance charges,the magnitude of the current which flows through either one of thecontrol members 10 correspondingly decreases.

Another important advantage of my invention is the wide range of currentcontrol obtainable. If it be assumed that it is desired to transmit tothe welding circuit l a current of relatively small magnitude where theimpedance of the Welding circuit is high, the phase shifter 23 may beadjusted to render the electric discharge devices l3 and I4 conductingnear the beginning of the positive half cycles of anode-cathode voltageapplied to electric valve means 3 and 4. Even though the impedance oftransformer 5 and the welding circuit l are relatively large, under thisassumed condition of operation, the impedance to the flow of ignitioncurrent to the control members is sufficiently low, by virtue of capacitance 34, to render the electric valve means 3 and 4 conductive. This isa decided advantage over the prior art arrangements where anodetypeexcitation circuits have been employed, because in the prior artarrangements the impedance of the load circuit materially limited theapplication of anode-type starting circuits.

While I have shown and described my invention as applied to a particularsystem of connections and as embodying various devices diagrammaticallyshown, it will be obvious to those skilled in the art that changes andmodifications may be made without departing from my invention, and I,therefore, aim in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, an alternating current supply circuit, a loadcircuit, transforming means having primary winding means and secondarywinding means connected to said load circuit, electric valve meansconnected between said primary winding means and said supply circuit andbeing of the type comprising an anode, a cathode, an immersion-ignitercontrol member in contact with said cathode and employing an ionizablemedium capable of supporting an arc discharge, an excitation circuitconnected between said anode and said control member, means forcontrolling said excitation circuit to determine the time in a cycle ofvoltage of said supply circuit at which said control member isenergized, and a capacitance connected across at least a portion of saidprimary winding means so that said control member is energized by thetransient current flow through said capacitor to insure sufficientcurrent through said control member to initiate conduction of said valvemeans independently of the time in the cycle of voltage of said supplycircuit that said control member is energized.

2. In combination, an alternating current supply circuit, a loadcircuit, a transformerhaving primary winding means and secondary windingmeans connected to said load circuit, a pair of reversely connectedelectric valve means connected in series relation with said primarywinding means and said supply circuit and each being of the typecomprising an anode, a cathode, an immersion-igniter control member incontact with said cathode and employing an ionizable medium capable ofsupporting an arc discharge, a pair of anode responsive circuits eachconnected between the anode and the control member of a different one ofsaid electric valve means and each comprising an electric dischargedevice having a grid, means for controlling said grids to render thedischarge devices conducting at predetermined times during a cycle ofvoltage of the supply circuit, and a capacitance connected across atleast a portion of said primary winding means so that the transientcharging current of said capacitor flows through the control members toinitiate conduction of said valve means irrespective of the impedance ofsaid load circuit and said transformer and the time in the cycle thatsaid control members are energized.

3. In combination, an alternating current supply circuit, a loadcircuit, transforming means having primary winding means and secondarywinding means connected to said load circuit, electric valve meansconnected between said supply circuit and said primary winding means andbeing of the type comprising an anode, a cathode, an immersion-ignitercontrol member in contact with said cathode and employing an ionizablemedium capable of supporting an arc discharge, an excitation circuitconnected between said anode and said control member and comprising anelectric discharge device of the controlled type having a control gridfor determining the time during a cycle of voltage of said supplycircuit at which current is transmitted to said control member, and acapacitance connected across at least a portion of said primary windingmeans so that the transient charging current of said capacitor flowsfrom said source through said electric discharge device, said controlmember and said cathode and insures initiation of conduction of saidvalve means regardless of the time in the cycle of voltage of the supplycircuit that said control member is energized.

4. In combination, an alternating current supply circuit, a loadcircuit, a transformer having primary winding means and secondarywinding means connected to said load circuit, a Pair of reverselyconnected electric valve means connected in series relation with saidsupply circuit and said primary winding means and being of the typecomprising an anode, a cathode, an immersion-igniter control member incontact with said cathode and employing an ionizable medium capable ofsupporting an arc discharge, a pair of excitation circuits eachassociated with a different one of said electric valve means and eachcomprising an electric discharge device connected between the anode andthe associated control member to transmit timed impulses ofunidirectional current thereto for initiating arc discharges between theanodes and associated cathodes, the discharge devices each comprising acontrol grid, means for energizing the control grids, tov determine thetime during a cycle of alternating voltage of said supply circuit atwhich said positive impulses of current are transmitted to said controlmembers, and a capacitance connected across at least a portion of saidprimary winding means to provide a relatively low impedance path for theflow of excitation current to said control members irrespective of theimpedance of said load circuit and said trans-- former to insure thesupply of sufllcient exciting current to said control members toinitiate conduction of said electric valve means regardless of the timein the cycle of the voltage of the supply circuit that said controlmembers are energized.

5. In combination, an alternating current supply circuit, a loadcircuit, transforming means having primary winding means and secondaryWinding means connected to said load circuit, electric valve meansconnected between said primary winding means and said supply circuit andbeing of the type comprising an anode, a cathode, an immersion-ignitercontrol member in contact with said cathode and employing an ionizablemedium capable of supporting an arc discharge, an excitation circuitconnected between said anode and said control member, and impedancemeans connected in series relation with said supply circuit and saidexcitation circuit to provide a path for the flow of excitation currentto said control member, the impedance of said path being substantiallyless than the impedance through said load circuit and of such a value asto pass sufiicient excitation current to said control member to enablesaid valve to be rendered conductive over substantially the full rangeof instantaneous values of anode voltage in any given positive halfcycle of said supply circuit.

6. In combination, an alternating current supply circuit, a loadcircuit, transforming means having primary Winding means and secondarywinding means connected to said load circuit, electric valve meansconnected between said primary winding means and said supply circuit andbeing of the type comprising an anode, a cathode, an immersion-ignitercontrol member in contact with said cathode and employing an ionizablemedium capable of supporting an arc discharge, an excitation circuitconnected between said anode and said control member and comprising anelectric discharge device, means for controlling the conductivity ofsaid discharge device, and impedance means connected in series relationwith said supply, said control member and said cathode, to provide arelatively low impedance path for the flow of excitation current to saidcontrol member irrespective of the time during the positive half cyclesof applied anode-cathode Voltage applied to said electric valve means at1 which said electric discharge device is rendered conductive,

LOUIS G. LEVOY, JR.

